1. Technical Feild
The present invention relates to a method of making a fluid dynamic bearing, and more particularly relates to a method of making a fluid dynamic bearing by sintering.
2. Discription of Related Arts
Due to request for low abrasion on rotational elements to achieve an extended life and for low extent of noise, fluid dynamic bearings (FDBs) have been used in fan motors, hard disk drive motors, or the like.
As shown in FIG. 10, in a typical FDB, a rotary shaft 100 is rotatably inserted into a sleeve 200 with a bearing clearance formed between the rotary shaft 100 and the sleeve 200. A plurality of dynamic pressure generating grooves 300 is formed on an inner peripheral surface of the sleeve 200. Lubricating oil is applied to the bearing clearance. A pressure is generated due to the pumping action of the dynamic pressure generating grooves 300 caused by the rotation of the rotary shaft 100. As a result, the rotary shaft 100 rotates in the sleeve 200 without radial contact with the sleeve 200.
In the FDB of FIG. 10, the dynamic pressure generating grooves 300 are V-shaped and also referrer to as herringbone type grooves.
Referring to FIG. 11, another kind of groove is shown, in which the sleeve forms a plurality of step structures 400 in an inner bore thereof. This kind of groove is referred to as step type groove.
In manufacturing the grooves, a tooling head is typically needed to extend into the bore of the sleeve. For example, in manufacturing the herringbone type grooves, a rotational speed and a linear feeding speed with respect to the sleeve are simultaneously applied to the tooling head, thereby forming the grooves that resemble the motion of the tooling head. When the sleeve is very small, manufacturing the grooves can be very difficult. It is generally acknowledged that the shape of the groove plays an important role in the establishment of the dynamic pressure. However, the difficulties in forming grooves restrain the commercially use of various grooves of complicated shape, even though these grooves have been experimentally proved to have advantages in the establishment of the dynamic pressure over the conventional grooves. Therefore, a heretofore-unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.